 |
Description  |
|
|
SUMMARY OF THE INVENTION HAVING BOGIE MOUNTED WHEELS
This invention relates to a vehicle having three or four ground-engaging
wheels on each side. More particularly it relates to a tractor wherein at
least two of the wheels on each side are mounted on a bogie which is
pivotably mounted on a shaft extending from the tractor's frame.
According to a first aspect of the present invention there is provided a
vehicle having on each side at least three ground wheels disposed one
behind the other with respect to the direction of normal travel of the
vehicle, at least two, but not all, of said wheels being mounted on a
common bogie which is coupled with the rest of the vehicle for pivotal
movement about a pivotal axis disposed between the axles of the wheels
mounted on the bogie, one of said ground wheels being pivotable relatively
to the rest of the vehicle about an upwardly extending steering axis. The
foremost and rearmost wheels are both driveable by the vehicle's engine
and are steerable. In one embodiment there are two intermediate wheels on
each side which are also steerable. The vehicle is provided in at least
one embodiment with two parallel longitudinally extending trains of gears
for driving the wheels, each train being connected to the tractor's engine
via a transmission and differential. In each embodiment, lifting devices
are provided at both the forward and rear ends of the vehicle and the
engine is disposed between the foremost and rearmost wheel axles.
For a better understanding of the present invention and to show how it may
be carried into effect, reference will now be made, by way of example
only, to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a tractor;
FIG. 2 is a plan view of the tractor shown in FIG. 1;
FIG. 3 is a side view of a second embodiment of a tractor;
FIG. 4 is a plan view of the tractor shown in FIG. 3;
FIG. 5 is a side view of a third embodiment of a tractor;
FIG. 6 is a plan view of the tractor shown in FIG. 5; and
FIG. 7 is a sectional view taken on the lines VII--VII in FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The tractor illustrated in FIG. 1 comprises a frame 1 supported by front
wheels 2 which can rotate about axes 3 and by rear wheels 4 which can
rotate about axes 5. The axes 3 are provided by a horizontal front axle
member 6 which is transverse of the intended direction of forward travel A
and is freely pivotable with respect to the frame 1 about a horizontal
pivotal axis 7 lying in the vertical central longitudinal plane of the
tractor. The axes 5 of the rear wheels 4 are provided by a horizontal rear
axle member 8 which is transverse of the direction A and is rigidly
secured to the frame 1 although it could be pivotable in the same manner
as the axle member 6. The front wheels 2 and the rear wheels 4 are all
steerable. For this purpose the front wheels 2 are pivotable about
upwardly extending king pins 9 with respect to the front axle member 6,
and the rear wheels 4 are pivotable about upwardly extending king pins 10
with respect to the rear axle member 8. The axes 3 of the front wheels 2
and the axes 5 of the rear wheels 4 are rigidly fixed with respect to
track arms 11 and 12 respectively, which are pivotally connected to
hydraulic steering cylinders which can be actuated by a driver of the
tractor and are fastened to the front axle member 6 and to the frame 1
respectively.
The frame 1 supports a driving engine 13 in the region between the axes 3
and 5, in the part of that region nearer the rear axes 5. This engine 13
is connected to drive the front wheels 2 and the rear wheels 4 through a
transmission 14. The transmission 14 comprises a clutch and a mechanical
or hydrostatic torque converter. The transmission 14 is disposed in front
of the engine 13.
Above the region between the axes 3 and 5 and nearer the axes 3 there is a
driver's cab 15 at the front of the tractor. The lower side of the cab 15
is farther from the ground than the top point of the front wheels 2. The
cab 15 contains a driver's seat 16 and a console 17 provided with a
steering wheel 18 as well as with other steering and control members of
the tractor. The seat 16 and the console 17 are fixed to one another and
are rotatable together about a vertical axis 19 located between the seat
16 and the console 17. The assembly of the seat 16 and the console 17 can
be turned about the axis 19 through 180.degree. and be fixed in either of
two positions, in one of which the driver faces forward and in the other
of which he faces to the rear, with respect to the direction A. When the
tractor is driven in the direction opposite to the direction A, the wheels
2 become the rear wheels. The transmission 14 is arranged in the space
below the bottom of the cabin 15 and above the frame 1.
At both the front and the rear, the frame 1 has three-point hitching
devices 20 and 21, which can be actuated from the driver's seat 16.
Beneath the frame 1, at a location approximately midway between the wheel
axes 3 and 5, there is a downwardly extending support 22 rigidly fastened
to each side of the frame 1. Near the lower end of each of the supports 22
is rigidly fastened a shaft 23 which projects in a direction perpendicular
to the vertical, longitudinal central plane of the tractor. The two shafts
23 project sideways from the frame 1. On the outermost end of each shaft
23 is mounted a wheel carrier 24 which is freely pivotable about its shaft
23. Each wheel carrier 24 is substantially horizontal and is parallel to
the central longitudinal plane of the tractor and its shaft 23 is located
approximately midway along the length of the tractor.
Near each end of each wheel carrier 24 there is a wheel axle designated by
reference numeral 25 forward, to the rear, which is perpendicular to the
central, longitudinal plane of the tractor. The axles 25 and 26 are the
same distance as each other from the shaft 23. The axle 25 has a wheel 27
of the tractor, and the axle 26 has a wheel 28. The wheels 27 and 28 are
only a small distance from one another.
The assembly comprising the wheel carrier 24 and its two or more wheels is
referred to from now on in this description as a bogie.
The front wheels 2 and the rear wheels 4 have the same diameter as each
other. The diameters of the non-driven wheels 27 and 28 located between
the wheels 2 and 4 are equal to one another, but smaller than the
diameters of the wheels 2 and 4; preferably they are about one-half the
diameter of the wheels 2 and 4. The bogie on each side of the tractor is
pivotable about the centerline of its shaft 23 independently of the bogie
on the other side of the tractor.
The construction described above allows the tractor, in operation and
particularly when negotiating bends, to follow the ground surface, since
the wheels 27 and 28 on each side of the tractor can assume positions
required by the ground surface by pivoting of the bogie with respect to
the frame 1. Furthermore the wheels 27 and 28 can effectively and evenly
support some of the weight of the tractor so that wheel pressure of the
steerable wheels can be reduced when travelling on weak soil. Not only do
the front wheels 2 pivot about the axis 7, but the steered rear wheels 4
make sufficiently firm ground contact to absorb the lateral forces
required for steering, since the wheels 27 and 28 turning about the shaft
23 hardly reduce the magnitude of the ground contact pressure applied by
the rear wheels 4 and originating from the weight of a machine hitched to
the lifting device 21. It is advantageous to dispose the wheels 27 and 28
at the smallest possible distance from one another.
The tractor shown in FIGS. 3 and 4 comprises a driver's cab 29 disposed
substantially midway along the length of the tractor. A driver's seat and
steering and control members are provided, these being constructed and
pivotally arranged in the same way as those in the first embodiment, and
they are designated by the same reference numerals.
An engine 30 is arranged in front of the driver's cab 29 on the tractor
frame and a transmission 31 comprising a clutch and hydraulic pump is
disposed behind the engine and beneath the driver's cab. The tractor in
this embodiment is particularly appropriate for working very large fields.
In order to provide a large range without refuelling, almost the whole
space above the frame and behind the cab 29 is available for fuel tanks.
At both front and rear the frame is provided with hitching devices 32, 33
respectively, which can be actuated by the driver. The tractor has, in
all, eight driven wheels, there being four wheels 34, 35, 36 and 37
arranged one behind the other on each side of the tractor. All of the
wheels 34 to 37 are drivable by means of hydraulic wheel motors, which are
powered by the hydraulic fluid pump provided in the transmission 31.
The leading wheels 34 and 35 and the trailing wheels 36 and 37 constitute
two separate groups. Since the structure of the two groups are identical,
only the trailing group comprising the wheels 36 and 37 will be described
in detail. Each of the wheels 36 and 37 is pivotable about an upwardly
extending king pin 38. The stub axle of each wheel has a rigidly secured
track arm 39, which extends away from the king pin 38, about which the
wheel is pivotable, in a direction away from the wheel. The king pin 38 of
each wheel is fastened to a carrier 40 at a free end of the carrier 40.
The carrier 40 extends away from the king pin 38 towards the vertical
central longitudinal plane of the tractor. Viewed on plan, the four arms
40 of the wheels 36, 37 on the two sides of the tractor form a cross and
are of equal lengths. These four arms 40, which extend substantially
parallel to a horizontal plane, are rigidly secured to one another at or
near the vertical central longitudinal plane of the tractor and are
pivotable together about a common horizontal pivotal shaft 41 which is
transverse of the vertical central longitudinal plane of the tractor. The
angle between the two arms 40 on the same side of the tractor frame is
about 100.degree. to 120.degree. in the embodiment shown, this angle being
chosen so that the surface of each arm 40 facing the wheel mounted on it
is substantially parallel to the vertical plane containing the inboard
surface of the wheel when the wheel is at full lock in one direction. The
crosswise interconnected arms 40 constitute together with the pivotal
shaft 41 a bogie.
In a modification of the tractor shown in FIGS. 3 and 4, the arms 40
located on each side of the tractor are separate from those on the other
side so that the arms of the two sides are independently pivotable. The
wheels 36 and 37 on each side of the tractor are, therefore, pivotable
together relatively to the wheels 36 and 37 on the other side about the
pivotable shaft 41.
All of the wheels of the two-wheel or four-wheel bogies are steerable from
the driver's seat 16. When negotiating a bend the four wheels visible in
FIG. 3 should have mutually different deflections from the positions for
straight-ahead travel, as is indicated in FIG. 4 by broken lines, since
the axes of the wheels, on both sides of the tractor, should intersect at
a single point. To achieve this, the two arms 40 of each of the two or
four bogies located on the same side of the vertical central longitudinal
plane of the tractor are provided with hydraulic cylinders 42 and 43. The
piston rod of the cylinder 42 is coupled with the track arm 39 of the
wheel 36 located nearer the center of the tractor, and the piston rod of
the cylinder 43 is coupled with the track arm 39 of the rear most wheel
37. The bore of the cylinder 42 is greater than the bore of the cylinder
43. The stroke of the piston of the cylinder 42 is smaller than the stroke
of the piston of the cylinder 43, the ratio of the strokes being equal to
the ratio of the sectional areas of the cylinder bores. On the other side
of the vertical central longitudinal plane of the tractor there is a
similar set of hydraulic cylinders 42 and 43. Each bogie for the wheels 34
and 35 is provided in a similar manner with four hydraulic cylinders
identical to the cylinders 42 and 43. The hydraulic pump of the
transmission 31 feeds all of the hydraulic cylinders 42, 43 by way of a
control valve which can be actuated by the driver.
The piston rods of the pistons in the hydraulic cylinders 42 and 43
preferably have ducts emerging from both ends of their cylinders, one end
of each piston rod being connected with the associated track arm 39.
During negotiation of a left-hand or a right-hand bend the working chamber
on one side of the piston in the cylinder 42 is connected by the control
valve with the hydraulic pump. The working chamber on the other side of
this piston communicates through a hydraulic duct with the working chamber
on one side of the piston in the cylinder 43, and the working chamber on
the other side of the piston in the cylinder 43 is connected by the
control valve with a reservior. During negotiation of a bend in the other
direction the situation is the reverse.
With the arrangement described, the volume of fluid displaced in the
cylinder 42 is equal to the volume of fluid displaced in the cylinder 43.
Since the sectional area of the bore of the cylinder 42 is larger than the
sectional area of the bore of the cylinder 43, the displacement of the
piston in the cylinder 42 is smaller than the displacement of the piston
in the cylinder 43, as a result of which the deflection of the wheel 36
during a bend is smaller than that of the wheel 37. It follows that the
maximum stroke of the piston in the cylinder 43 is proportionally larger
than the maximum stroke of the piston in the cylinder 42. This control
arrangement is provided on both sides of the longitudinal central plane of
the tractor and on all of the bogies. The volume of fluid supplied per
unit time to the cylinders 42 and 43 located on the outer side of the bend
exceeds the volume of fluid supplied to those on the inner side of the
bend. This effect varies with the deflection of the wheel 18 and is
achieved by the control valve, but as an alternative it could be achieved
by means of a conventional mechanical coupling between the track arms 39
of two wheels mounted on the same bogie and located directly opposite one
another on the two sides of the tractor frame. All of the steerable wheels
are controlled by the steering wheel 18.
In this embodiment the steerable wheels are themselves mounted on bogies,
while the same advantages are obtained as in the embodiment of FIGS. 1 and
2. During negotiation of a bend, all of the wheels can remain in contact
with the ground so that maximum ground contact pressure and driving force
are exerted by each of the steered and driven wheels. This is, of course,
particularly important if the tractor shown in FIGS. 3 and 4 is to make
bends of very small radius. The weight of machines carried by the hitching
devices 32 and 33 is distributed in an optimum manner along all wheels of
each bogie, since this weight is transferred to the wheels through the
pivotal shaft 41 located centrally between the wheels of each bogie.
The tractor illustrated in FIGS. 5, 6 and 7 has on each side of its frame,
three wheels arranged one behind the other with respect to the direction
of normal forward travel A. This tractor has front wheels 44, the wheel
axles 45 of which are pivotable about upwardly extending king pins 46 and
are fastened to a substantially horizontal front axle member 47 extending
transversely of the direction A. The front axle member 47 is pivotable
relatively to the frame about a horizontal pivotal shaft 48, which is
located in the vertical central longitudinal plane of the tractor. The
front axle member 47 is provided with a hydraulic cylinder for steering
the front wheels 44.
A frame member 49 of the tractor is arranged symmetrically to the vertical
central longitudinal plane of the tractor. It is narrow compared with the
overall width of the tractor, its width being 9 to 14% of the overall
width of the tractor.
At a position in front of the rear end of the frame member 49, a support 50
is fastened to the bottom of the frame member. This support 50 carries a
shaft 51, which extends horizontally and perpendicular to the vertical
central longitudinal plane of the tractor. The shaft 51 projects to both
sides beyond the frame member 49. A carrier beam comprising a wheel
carrier 52 is mounted freely pivotably about each of the two ends of the
shaft 51 projecting beyond the frame member 49. The wheel carriers 52
extend parallel to the frame member 49. The pivotal connection of each
wheel carrier 52 with its shaft 51 is midway along the length of the wheel
carrier 52. Each wheel carrier 52 is provided at each end with a support
53 forward, and 54, to the rear, respectively, each of which extends
perpendicular to the vertical central longitudinal plane of the tractor.
The leading support 53, with respect to the direction A, is provided at
its outer end with a wheel axle 55, on which a leading rear wheel 56 is
freely rotatable. The trailing support 54 is provided at its outer end
with an upwardly extending king pin 57, on which a wheel axle 58 is
pivotable. A trailing rear wheel 59 is rotatably journalled on the wheel
axle 58. The trailing rear wheels 59 are steerable in a similar manner to
the front wheels 44 by means of a hydraulic steering cylinder (not shown)
fastened to the associated support 54. The intermediate, leading rear
wheels 56 are not steerable and are not drivable. The wheels 44, 56, 59
all have the same diameter. The wheel carrier 52 on each side of the
vertical central longitudinal plane of the tractor, together with the
supports 53 and 54 rigidly secured thereto and the shaft 51 constitutes a
bogie. The bogies on the two sides of the tractors, which together
comprise a cradle frame part, are pivotable independently of one another
about the centerline of the shaft 51 with respect to the frame member 49.
At about the same level along the length of the tractor as the leading rear
wheel 56, there a driving engine 60 of the tractor which is mounted on the
frame member 49. A transmission 61 is disposed in front of, and coupled
with, the engine 60. This transmission comprises a driver-actuable clutch
and a torque converter. In front of the transmission 61 there is a
differential gear 62 which is driven by the torque converter. The
transmission 61 and the differential gear 62 are disposed beneath a
driver's cab 63 at the front of the tractor at the level of the front
wheels 44 and above the space between the wheels 44 and 56. The cab 63, as
before, comprises a driver's seat 16 and a console 17 provided with a
steering wheel 18 and other steering control members of the tractor. The
assembly of the seat 16 and the console 17 is again pivotable and fixable
in either of two positions about the vertial pivotal axis 19 located
between the console and the seat as in the embodiment of FIGS. 1 and 2.
When travelling in the direction opposite the direction A, the wheels 44,
constitute driven, steerable wheels of the tractor.
At both front and rear, the tractor frame has three-point hitching devices
64 and 65, which can be actuated from the driver's seat 16.
The frame member 49, which extends from ahead of the front axle 45 to
behind the rear axle 58, is assembled from two hollow beams 66 and 67
arranged side by side with a short gap between them, one on each side of
the central vertical plane of the tractor. The height of each of these
hollow beams is a few times larger than the width thereof. The bottom
surfaces of both of the hollow beams are rigidly secured to a
comparatively rigid carrying plate 68 (FIG. 7) covering the whole width of
the frame member 49.
The bottom of the differential gear 62 is fastened to the top surfaces of
the two hollow beams 66 and 67. The two output shafts of the differential
gear 62 drive pinions (not shown) are arranged side by side with a gap
between them, the rotary axes of these pinions being perpendicular to the
central vertical plane of the tractor. Each of these two pinions is in
mesh with a pinion 69 which has straight teeth and is housed in a
respective one of the hollow beams 66 and 67 (FIG. 5). The axes of these
pinions 69 coincide and are perpendicular to the central vertical plane of
the tractor. The pinions 69 are journalled separately in the respective
hollow beams 66 or 67. The pinions 69 each mesh with spur pinions 70,
which are disposed in front of and behind the pinion 69. All of the
pinions 70 have the same diameters and are rotatable about shafts
accommodated in the hollow beams 66 and 67 respectively, these shafts
being parallel to the rotary shaft of the associated pinion 69. The rotary
axes of the pinion 69 and 70 lie in a horizontal planne perpendicular to
the central vertical plane of the tractor. Each of the hollow beams 66 and
67 thus has a separate gear train comprising the pinions 69, 70 and, owing
to the differential drive, the speed of the pinions in the hollow beam 66
may differ from the speed of the pinions in the hollow beam 67. The pitch
circles of all of the pinions 69, 70 are the same.
The leading pinion 70 in the hollow beam 67 drives the front wheel 44
located on the right-hand side of the tractor, viewed in the direction of
travel A, and the leading pinion 70 in the hollow beam 66 drives the other
front wheel 44. Similarly, the trailing pinion 70 in the hollow beam 67
drives the trailing rear wheel 59 located on the right-hand side of the
tractor, and the trailing pinion 70 in the hollow beam 66 drives the other
rear wheel 59. FIG. 7 illustrates the drive of the right-hand front wheel
44. The drive of the other wheels 44 and 59 is performed in a similar
manner.
The rotary shaft of the leading pinion 70 in the hollow beam 66 is extended
to the outside of the beam as a shaft 71 (FIG. 7). To the outermost end of
the shaft 71 is fastened one member of a universal joint 72, by means of
which a telescopic shaft 73 can be driven, this shaft being located
substantially over the wheel axle 45. The end of the shaft 73 away from
the univeral joint 72 is drivably connected by means of a second universal
joint 74 with a shaft 75, which may form part of the joint 74. The shaft
75 is integral with a spur pinion 76, the central vertical plane of which
substantially coincides with the central vertical plane of the wheel 44.
The shaft 75 of the pinion 76 is journalled in one or more bearings 77,
the outer races of which are supported by an extension 78 of a rigid fork
78A, this extension being inclined inwardly from top to bottom away from
the bearings 77. The fork piece 78A is rigidly secured to the wheel axle
45 and supports the wheel 44 pivotably on the king pin 46. The pinion 76
meshes with a pinion 79, which is rotatable about the end of the wheel
axle 45. To the outboard side of the pinion 79 is secured a wheel disc 80,
the periphery of which is provided with a rim 81 of the wheel 44.
In operation, the two gear trains located in the two hollow beams 66 and 67
are driven through the differential gear 62 and the transmission 61 by the
engine 60, the differential gear providing, as is conventional, different
speeds of rotation of the wheels during negotiation of bends. The leading
and trailing pinions 70 in the hollow beams 66 and 67 drive the shafts 75
and hence the pinions 76 through the shafts 71 and the telescopic shafts
73. The diameter of the pitch circle of each pinion 76 is substantially 15
to 25% of the diameter of the pitch circle of the pinion 79. The torque
transmitted by the telescopic shaft 73 is, therefore, appreciably lower
than the torque applied by the wheels 44, 59.
As in the previous embodiments, all of the wheels located on one side of
the tractor can follow the ground surface, since the front wheels 44 are
pivotable about the wheel axle 48, and the wheels 56 and 59 of each bogie
are pivotable together about the centerline of the shaft 51. The weights
of machines attached to the lifting devices 64 and 65 are distributed over
all of the wheels, while the load on each set of rear wheels 56 and 59 is
applied at the shaft 51 located centrally between the wheels. Moreover,
during negotiation of bends, sufficient ground pressure is applied to the
steered and driven rear wheels 59 of the tandem carriage to exert the
required lateral forces, even with tractors for which at least three
wheels on each side of the tractor are required for travelling on weak
soil in order to avoid sinking into the ground; this is true also for the
preceding embodiments. In all embodiments all wheels located on one side
of the tractor may be replaced by a double set of wheels. Furthermore, in
all embodiments, the distance between the axes of a bogie is smaller than
the sum of the diameters of two wheels which are part of the bogie and
disposed one behind the other.
Although various features of the vehicles described and illustrated in the
drawings will be set forth in the following claims as inventive features,
it is to be understood that the invention is not necessarily limited to
these features and may encompass all features that have been described
both individually and in various combinations.
* * * * *
|
|
 |
|
 |
Description |
|
